This invention is directed to rare-gas hydrogen-halide excimer lasers, and in particular to the gas mixtures for these excimer lasers.
The long term, stable operation of rare-gas halide excimer lasers is a necessary prerequisite to their use as reliable tools in industrial applications. The discharge parameters and circuit characteristics of electric discharge excimer lasers have been examined, however, it has been determined that the effects of gas chemistry in these lasers is also important.
The combination of gas recycling and gas additives in pulsed infrared lasers such as CO.sub.2 and HF have been reported by C. Willis, and J. F. Purdon in the J. Appl. Phys. 50, 2539 (1979), and by C. Willis, M. Dosi and D. J. James in the Rev. Sci. Instr. 50, 622 (1979), respectively. These have led to significant reductions in operation costs. Similar efforts with rare-gas halide lasers have been described by M. A. Ackerman and R. A. Tennant in the Proceedings of the Topical Conference on Excimer Lasers, Charleston, S.C. (1979); by P. M. Johnson, N. Keller and R. E. Turner, Applied Physics Letters 32, 291 (1978), and by C. P. Christensen, Applied Physics Letters 30, 483 (1977). These typically employ gas recycling in an external loop where the halogen donor and reactive impurities are removed with a sequence of getter traps; subsequent introduction of the pure halogen donor leads to a revitalized gas mixture.